S1·E36 Return of Cassandra

While conducting a training exercise, the Centurions come under attack from Doc Terror's forces. Ace is rescued by his old acquaintance, Cassandra Cross, the witch. The Centurions decide to attempt to duplicate her powerful abilities by studying her on board Skyvault. But once connected to Skyvault's computers, she turns off the defense systems and introduces herself as Lilith Cross, Cassandra's twin sister. With no defense systems operative, Doc Terror beams on board Skyvault. Ace manages to escape using the magical white rose given to him by Cassandra, and beams to Earth. He finds Cassandra trapped by Lilith's magic, and frees her. Together, they go back to Skyvault, and attempt to free the other Centurions.

Science Lesson: Herbal medicine by Crystal.